1. Field Of The Invention
This invention relates to stripping compositions particularly useful for stripping paints, varnishes, enamels, photoresists and the like, from various substrates such as, for example, from wood or metal substrates. This invention also relates to the use of such stripping compositions to strip paint, varnishes, enaamels, photoresists and the like, from various substrates.
2. Description Of The Prior Art
Stripping compositions used for removing coatings from substrates have for the most part been highly flammable compositions, compositions generally hazardous to both humans and the environment and compositions which are reactive solvent mixtures evidencing an undesirable degree of toxicity. Moreover, these stripping compositions are not only toxic but their disposal is costly since they must be disposed of as a hazardous waste. In addition, these stripping compositions generally have severely limited bath life and, for the most part, are not recyclable or reusable.
Generally, compositions containing chlorinated hydrocarbons and/or phenolic compounds or other highly caustic and corrosive materials have been employed as stripping compositions for stripping paints, varnishes, lacquers, enamels, photoresists, powder coatings and the like, from substrates such as wood or metal. Hot caustic compositions are generally employed to remove coatings from metals and methylene chloride compositions to remove coatings from wood. In many cases, the components of the stripping compositions are relatively toxic reactive solvent mixtures and thus must be subject to stringent use conditions and require hazardous chemical handling procedures and wearing of safety garments and apparel by users so as to avoid contact with the stripping compositions.
Additionally, because many of the toxic components of such stripping compositions are highly volatile and subject to unduly high evaporation rates, the stripping compositions require special human and environmental safety precautions to be taken during storage and use of said compositions.
U.S. Pat. No. 4,276,186 to Bakos et al discloses a cleaning composition which includes N-methyl-2-pyrrolidone and an alkanolamine. However, in a comparative study, applicant has found that the use of N-methyl-2-pyrrolidone does not provide a broad spectrum of cleaning as is capable with the composition of the invention.
U.S. Pat. No. 4,617,251 to Sizensky discloses a stripping composition which is prepared with a select amine and an organic polar solvent. The composition is formed utilizing from about 2 to about 98% by weight of amine compound and about 98 to about 2% of an organic polar solvent. There is specifically disclosed a composition prepared with diethanolamine and N,N-dimethylacrylamide in a percent ratio of 60/40. The applicant has discovered that in order to obtain a stripping composition which have a broad spectrum of cleaning capabilities for resist-coated substrates, the use of N-methylalkanols which are straight chained together with specific amides in which the amide is present in the amount of 85 to about 99% by weight, is required.
Recently, OSHA, EPA and other similar federal, state and local governmental regulatory agencies have advocated a shift toward use of more human and environmentally compatible stripping compositions and stripping methods that are not subject to the aforementioned drawbacks and problems.
Moreover, heretofore available stripping compositions have required unduly long residence times or repeated applications in order to remove certain coatings. In addition, various coatings have resisted removal from certain substrates with these heretofore available stripping compositions. That is, these previously available stripping compositions have not provided adequate or complete removal of certain hard-to-remove coatings from various substrates.
It is, therefore, highly desirable to provide stripping compositions that exhibit substantially no human or environmental toxicity, are water miscible and are biodegradable. It is also desirable to provide stripping compositions that are substantially non-flammable, non-corrosive, evidence relatively little, if any, tendency to evaporate and are generally unreactive and also of little toxicity to humans and are environmentally compatible. It would also be most desirable to provide stripping compositions that are recyclable, if desired, and thus available for extended bath life and multiple use. It is also desirable that stripping compositions be provided that permit the stripped coatings to be collected and removed as solids for easy disposal.
Moreover, it would be desirable to provide stripping compositions that have a high degree of stripping efficacy and particularly such high degree of stripping efficacy at lower temperatures than generally required with prior stripping compositions.
It is also highly desirable that stripping compositions be provided that exhibit very low vapor pressure at elevated temperatures, thereby significantly reducing evaporation and thus contamination of the atmosphere.
Additionally, it is highly desirable that such stripping compositions be provided that are effective and efficient stripping compositions for removal of coatings from substrates that heretofore have resisted ready removal with conventionally available strippers.
It is also desirable that effective stripping compositions be provided that are devoid of undesirable chlorinated or phenolic components and which do not require the use of hot caustic components. Highly desirable are stripping compositions and use thereof that are not considered undesirable by regulatory agencies overseeing their production and use.
It is also most advantageous that stripping compositions be provided with the above-identified desirable characteristics which evidence synergistic stripping action in that the mixtures of components provide stripping efficacy and stripping results not always obtainable with the individual components.